diff --git a/OpenUtau/Controls/ExpressionCanvas.cs b/OpenUtau/Controls/ExpressionCanvas.cs
index 901ff5def..2146a606f 100644
--- a/OpenUtau/Controls/ExpressionCanvas.cs
+++ b/OpenUtau/Controls/ExpressionCanvas.cs
@@ -94,9 +94,27 @@ public ExpressionCanvas() {
 
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change) {
             base.OnPropertyChanged(change);
+            if (change.Property == KeyProperty || change.Property == PartProperty) {
+                InvalidateMeasure(); 
+            }
             InvalidateVisual();
         }
 
+        protected override Size MeasureOverride(Size availableSize) {
+            double requiredHeight = 0;
+            if (Part != null && !string.IsNullOrEmpty(Key)) {
+                var project = DocManager.Inst.Project;
+                if (project.tracks[Part.trackNo].TryGetExpDescriptor(project, Key, out var descriptor)) {
+                    if (descriptor.type == UExpressionType.Options) {
+                        requiredHeight = descriptor.options.Length * 24; 
+                    }
+                }
+            }
+            return new Size(
+                double.IsInfinity(availableSize.Width) ? 0 : availableSize.Width,
+                requiredHeight
+            );
+        }
         public override void Render(DrawingContext context) {
             base.Render(context);
             if (Part == null) {
@@ -118,7 +136,7 @@ public override void Render(DrawingContext context) {
             double leftTick = TickOffset - 480;
             double rightTick = TickOffset + Bounds.Width / TickWidth + 480;
             double optionHeight = descriptor.type == UExpressionType.Options
-                ? Bounds.Height / descriptor.options.Length
+                ? Math.Max(Bounds.Height / descriptor.options.Length, 24.0)
                 : 0;
             if (descriptor.type == UExpressionType.Curve) {
                 var curve = Part.curves.FirstOrDefault(c => c.descriptor == descriptor);
diff --git a/OpenUtau/Controls/PianoRoll.axaml b/OpenUtau/Controls/PianoRoll.axaml
index 7f7ff44bd..885e7b95f 100644
--- a/OpenUtau/Controls/PianoRoll.axaml
+++ b/OpenUtau/Controls/PianoRoll.axaml
@@ -659,18 +659,20 @@
                           Part="{Binding NotesViewModel.Part}"
                           Key="{Binding NotesViewModel.SecondaryKey}"
                           ShowRealCurve="False"/>
-      <c:ExpressionCanvas Grid.Row="5" Grid.Column="1"
-                          IsVisible="{Binding NotesViewModel.ShowExpressions}"
-                          Margin="0,24,0,0"
-                          Bounds="{Binding NotesViewModel.ExpBounds, Mode=OneWayToSource}"
-                          TickWidth="{Binding NotesViewModel.TickWidth}"
-                          TickOffset="{Binding NotesViewModel.TickOffset}"
-                          Part="{Binding NotesViewModel.Part}"
-                          Key="{Binding NotesViewModel.PrimaryKey}"
-                          ShowRealCurve="True"
-                          PointerPressed="ExpCanvasPointerPressed"
-                          PointerMoved="ExpCanvasPointerMoved"
-                          PointerReleased="ExpCanvasPointerReleased"/>
+      <ScrollViewer Name="ExpScrollViewer" Grid.Row="5" Grid.Column="1" Margin="0,24,0,0" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Disabled">
+          <c:ExpressionCanvas IsVisible="{Binding NotesViewModel.ShowExpressions}"
+                              Bounds="{Binding NotesViewModel.ExpBounds, Mode=OneWayToSource}"
+                              TickWidth="{Binding NotesViewModel.TickWidth}"
+                              TickOffset="{Binding NotesViewModel.TickOffset}"
+                              Part="{Binding NotesViewModel.Part}"
+                              Key="{Binding NotesViewModel.PrimaryKey}"
+                              ShowRealCurve="True"
+                              MinHeight="{Binding #ExpScrollViewer.Bounds.Height}"
+                              VerticalAlignment="Top"
+                              PointerPressed="ExpCanvasPointerPressed"
+                              PointerMoved="ExpCanvasPointerMoved"
+                              PointerReleased="ExpCanvasPointerReleased"/>
+      </ScrollViewer>
       <ListBox Grid.Row="5" Grid.Column="1" HorizontalAlignment="Left" VerticalAlignment="Top" Classes="toolbox"
                SelectedIndex="{Binding CurveViewModel.CurveToolIndex}" IsVisible="{Binding NotesViewModel.ShowCurveToolbox, Mode=OneWay}">
         <ListBox.ItemsPanel>